Maximizing Fall and Winter Grazing of Beef Cows and Stocker Cattle

Bulletin 872-98

Soil Characteristics and Fertility for Grazing

Soils are a fixed natural resource that can not be greatly altered. The plant and animal species need to be matched to the soil resource on a given landscape. The management level and forage production system also need to be adapted to match the soil resource base. The landscape indicates the soil types, water-runoff patterns, erosion potential, and air movement. Cold air flows into swales, and ridgetops provide positive air movement in the summer.

The Soil Survey for your county will help you to identify the soil map unit and its characteristics that will affect your grazing system. Information on the soils for the property you manage is available from the local office of the Natural Resources Conservation Service (formerly the Soil Conservation Service or SCS). Soils are assigned pasture and hayland suitability groups. Soils assigned the same suitability group require the same general management and have about the same potential productivity.

The Pasture and Hayland Soil Suitability Groups include Group A that has few limitations affecting the management and growth of forage plants. Soils in Group B are limited by droughthiness because of sand and stones throughout the soil. Group C soils are normally wet due to high water tables or soils that are saturated during the growing season. These soils generally respond to subsurface drainage. The soils in Group D are organic or muck soils and are generally not used in forage production. Group E soils have a restricted root zone of less than 20 inches, while Group F soils have a root zone of less than 40 inches but greater than 20 inches. There are just a few soils on strip mines in Ohio that have unfavorable chemical properties; these soils would be Group G. Group H soils are unsuitable for forage production because of toxic chemical properties or very steep slopes.

There are other soil properties affecting grazing systems and forage production that should be considered.

1. The surface texture and organic matter content affects new seedling establishment, water infiltration rate, and plugging during wet conditions.

2. The slope affects erosion potential and grazing patterns. Forage production on very steep slopes (i.e., greater than 25%) is extremely limited and use of farm equipment on these areas should be limited. As the slope angle increases, animal movement is generally more along the slope. Livestock trails can concentrate runoff and increase erosion and gully formation. Extreme care must be exercised when utilizing steep areas to maintain or increase productivity.

3. The shrink-swell potential and frost action affects plant crowns and over-wintering losses in the plant stand. The number of freeze-thaw cycles will be much greater on a south-facing slope than a north-facing slope. This greatly increases heaving potential on clay soils.

4. The aspect of a hillside or facing direction of the slope can produce up to a 50% difference in production. South-facing slopes will begin forage growth earlier in the spring and continue later into the fall because the angle of the sun is more perpendicular to a south-facing slope than a north-facing slope. North-facing slopes will be more productive during mid summer while south-facing slopes are prone to droughthiness. On landscapes where these differences are greatest, different species may be selected to match soils and slope aspect. The differences in north- and south-facing slopes can be useful in designing a grazing-system paddock layout.

5. The permeability and drainage of the soil determines the type of plant species that can grow and the ability to graze this area during wet conditions. While alfalfa requires deep, well-drained soils, birdsfoot trefoil will tolerate wetter soils. Matching your soil characteristics to adapted forage species and cultivars is extremely important to a productive forage system.

Soil nutrient management is an important part of pasture management. Soil or plant tests should be taken at least once very three years to monitor nutrient levels. Soil pH should be maintained at 6.0 for grass-legume pastures with neutral to alkaline subsoils and at 6.5 - 6.8 when subsoils are acid as is found in most of the unglaciated portion of southern and eastern Ohio. Bray P1 phosphorous levels should be maintained at 30 lbs. per acre for Kentucky Bluegrass and 50 lbs. per acre for tall grass-legume mixtures. The warm-season grasses are less responsive to pH and fertility levels. Potassium levels should be maintained at or above 150 lbs. per acre K2O plus five times the CEC level of the soil. For a soil with a CEC of 10, K2O levels should be 150 + 5 x 10 or 200 lbs. per acre. To convert Bray P1 or K2O levels to ppm, divide by two. High levels of potash in combination with low levels of magnesium can cause grass tetany. A balanced fertility program can provide a balanced diet to the grazing animals.

Fertilizers can be used as a management tool to increase forage production just before times of slow plant growth. Applying fertilizer, particularly nitrogen, in the early and late summer increased production into the summer and fall. Management-intensive grazing improves manure distribution which provides a more balanced fertility program while allowing for nutrients to be recycled and reused repeatedly. High levels of nutrient transfer can occur around shade and water. These nutrients must then be purchased and applied to deficit areas. Supplement feed (i.e., hay or grain) can be fed in areas needing additional fertility. This is a very efficient way to Fertilize pasture areas difficult to cover with a fertilizer spreader.